The present invention relates generally to an automatic air conditioning system for an automotive vehicle, which can operate in various operational modes including a defrosting or demisting mode in which the temperature of air discharged through a defroster nozzle or nozzles is controlled in accordance with a set temperature. More particularly, the invention relates to a blower control system for an automatic air conditioning system which can operate in a demisting mode.
Throughout the disclosure, the term "DEMIST mode" will be used to refer to the case in which air is discharged only through the defroster nozzle and the floor or lower air outlet. The temperature of the air to be discharged through the defroster nozzle and the lower air outlet is adjusted according to a set temperature.
In general, an automotive automatic air conditioning system is operable either in MANUAL mode or AUTO mode. A DEFROST mode can be selected manually to discharge warm or hot air through a defroster nozzle toward a front windshield in order to defrost or defog same. When the DEFROSTER mode is selected, a temperature-controlling air mix door is actuated to its full-heating position to adjust the temperature of the air to be discharged through the defroster nozzle to the highest possible temperature. In addition, when the DEFROSTER mode is selected, a chest vent and a floor vent are shut so that the defrosting or defogging air is discharged only through the defroster nozzle. As a result, the feet of the occupant of the vehicle cabin may become cold.
Additionally, if the air conditioning system is operated in the DEFROSTER mode, a compressor actuation clutch is disconnected so that the engine output will not be transmitted to the compressor. Therefore, humidity in the vehicle cabin will not be controlled. This, in turn, means when the air conditioner operates in the DEFROSTER mode, the front windshield may at first frost or fog over, degrading visibility.